Agglomeration by sulfonated reagents in magnetic recovery of iron ores



Mm July 1, 1m

AGGLOMERA'I'ION AGENTS IN IRON 0328 Eur Conrad Herhenhofl,

signor to American MAGNETIC RECOVERY OF Stamford, com, a-

d Company, New

York, N. Y., a corporation oi Main No Drawing. Applicatio a June 1, 1945,

Serial No. 59 1446 'This' invention relates to the beneiiciation of 7 Claims. (91. eta-s) mineral values of low grade iron ores by a novel combination of chemical pretreatment and mag netic separation. Broadly, the process is applicable to the beneflciation of oxide minerals from iron ores containing an excess of acidic or silicious gangue. More particularly, the invention is especially well adapted to the treatment of ores in which a non magnetic oxide constituent/ occurs with a magnetic or a magnetizable oxide constituent.

. Increasing amounts of various lower grade ores are becoming industrially important ,because of the decreasing supply of high grade ores. Typical illustrations are found in-iron, ores. Many deposits comprise ores which are too low in iron and too'high in sillco-bearing gangue to be suitthey must be beneiiciated in some manner. Calcium carbonate and other alkaline earth oxide and carbonate minerals also frequently occur in other iron ores. These maybe even to a certain extent desirable, but if the' iron content is too low, it must be raised by removing a portion of these minerals. The problem, then, is one reducing impurities and r content to as high a de ee as practicable.

Beneficiation has been attempted by many different procedures, depending upon the ore. In some cases the nece 'ry increases in'grade may be made simply by crushing and washing the ore. Where the mineral values and the gangue are associated in such manner that this cannot be able for use as blast furnace feed. To be useful ising the mineral value done, the mineral values must be released by crushing or grinding. Heavy-media separation has proved particularly useful in the treatment of particle sizes down .to about 1; inch. Other naturally occurring .ores require reduction to smaller sizes, as low as -48 mesh down to fines, to unlock the objectionable gangue, and various froth flotation procedures have been developed for use in beneficiatlng these finely ground ores. It is with those ores which must be reduced to 8-12 mesh or smaller that the present invention is particularly concerned.

In the past it has been proposed to beneiiciate f nely ground, low-grade, non-magnetic ores by magnetic treatment rather than by froth flotation. Perhaps the best of such processes consists in mixing magnetically-susceptible particles with a ground ore of non-magnetic minerals and treating an aqueous pulp of these mixtures with a fatty acid, such as oleic acid, apparently to distribute a film 01' finely divided magnetic particles over the surface of the non-magnetic particles. The treated pulp is then usually deslllned, at least the sands are dried and the dried material subiected to magnetic separation, the magnetically susceptible portion being thereby withdrawn and carrying with it the 'non magnetically susceptible material associated therewith. This procedure is of little use except in conjunction with flotation or some similarly more effective operation. When used alone it does not give either a particularly good recovery or a particularly good degree of concentration. It is also subject to several other objections in that it involves separation of sands and slimes and that it requires a drying operation before treating by dry magnetic separation.

Nevertheless, a practicable magnetic separation is commercially very desirable. For treating many ores, it would possses definite advantages over froth flotation, both technically and econom'lcally. It is, therefore, the principal object of the present invention to develop a magnetic beneilciating process which is not subject to the objectionable features noted above.

Because many iron ores naturally occur as admixtures of non-magnetic iron oxides, such as hematite, martite and the like, with such magnetic oxides a magnetite, the process will be dis-' cussed in connection therewith. In general, the desired object is obtained by treating an aqueous pulp of the ore with a suitable sulfonated agglomerating agent and then subjecting the conditioned pulp directly to magnetic separation. This eliminates much of the subsequent desliming problem and the necessity for drying as is taught in the prior art. Equally important, it not more so,

the process when used alone yields products which are satisfactory in both grade and recovery.

According to the present invention the sulfohated agglomerating agents which may be'used in accordance therewith may be quite widely varied. Among the various reagents suitable for the purpose are such materials as the sulfonated petroleum hydrocarbons, both the so-called watersoluble green acid and oil-soluble mahogany M d, types obtained in the reiining o1 petroleum a scam;

lubricating oils; sulfonated fatty acids, such-"as lauric, oleic, linoleic, cocoanut fatty acids, soyafatty acids and the like: sulfonated abietic acids; sulfonated naphthenic acids; such sulfonated. saponifiable oils, i. e., esters of polyhydric alcohols and long chain palm oil, and the like; sulfonated crude and refined talloel and mixtures thereof, also sulfonated, organic residues as still bottoms. pitches,

distillation by-products, oils recovered ous processes and the like.

Throughout this case in referring to petroleum sulfonates, the terms sulfonate and sul- -fonated" are used very loosely. Many of these products are mixtures of indeterminate chemical constitution and often a large portion of the combined acid groups are actually sulfate groups rather than sulfonic acid groups. Thi i largely due to their original which, as noted above, is in the refining of petroleum lubricating oil stocks. As shown for example in U. 8. Patent 2,331,049, their principal source is as by-products from the refining of petroleum lubricating oil fractions in the course of treatment with fuming sulfuric acids or sulfuric acids. Hence, the terms will be used not in their strict chemical sense but in the general sense in which they are employed in the art.

These sulfonated reagents may be used in new tral or alkaline circuit if so desired, in which case suitable alkaline conditioning or modifying agents, such as soda ash, caustic soda, sodium silicate, and the like, may be added. However, most of the problems which the present invention was designed to overcome are present in the beneficiation of many iron ores, and the best results with such ores appear to be obtained in acidic circuit. That consideration must also be applied. Almost any acidic agent, which is itself or-yields a product which is an acid having a fairly high dissociation constant, preferably greater than about may be used. For practical purposes, sulfuric acid, because of its low cost and availability, is an acidic material which is attractive from a commercial point of view. Ordinarily, a sufflcient amount should be used so that a pH of between about 5.5 and 1.5 is produced.

Conditioning with the reagents, which is an important feature of the present invention, often presents a problem of physical distribution. This is particularly acute both where the reagent is not readily dispersible in water and where the collector is very soluble. In such cases an oiling agent may profitably be used as an adjunct. Unsaponifiable hydrocarbon oils such as fuel oil give excellent results and their low price makes them very attractive in most locations. In practice they are to be preferred. However, other oils such as glyceride oils, for example, cocoanut oil, linseed or cottonseed oils, can be made to work satisfactorily. Certain fatty acids of oily nature if necessary also may be used in acid circuit. The amount of oiling, however, depends very largely on the particular reagents used and may vary from a small amount up to several pounds per tom With every reagent combination there is an optimum range of oiling agent. This range is not critical and is not the same in every case. The optimum proportions should be determined in each case, but once determined, no operating difficulties result since the range is broad enough to take care of ordinary fluctuations in operation.

In general, the principal process step of the from varialiphatic acids of animal and ve 7 etable origin, as corn oil, fish oil, cottonseed oil,

ceptible material.

present inventionjare exceedingly'sir'nple. While the overall procedure may be varied, several steps are characteristic. First, if the ore contain no magnetically susceptible material, the latter must 6- be provided. Second, an aqueous pulp of the /ore. previously reduced to a sufficient fineness to liberate essentially the mineral values, is conditioned to cause agglomertaion of the magnetically susceptible and the desired non-magnetically sus- Third, the conditioned pulp is, without other treatment, subjected to a strong magnetic influence whereby the agglomerated or ilocculated material is drawn therefrom.

The second and third steps are always'present whether the ore is one which naturally contains material of high coercive force and remanence or whether such material is artificially incorporated therein. They constitute common features between such processes and those in which the magnetic and non-magnetic mixture constitutes the desired concentrate, in which the magnetic material is subsequently separated from the nonmagnetic portion, which itself is the desired concentrate, and those in which the magnetic material is separated and reused. The process may be applied not only to naturally-occurring ores but also to products from previous beneficiation such as tabling, flotation and the like.

As has been noted, the process requires chemical treatment of the ore in an aqueous pulp. The

extent to which the ore is reduced in size before pulping is determined largely by the degree of crushing or grinding required to free the mineral values. The process is not limited to the relatively fine grinding normally required for froth flotation. It can be applied to particle sizes which are too small for emclent beneficiation by heavy-media separation but too large for froth flotation: i. e., minus 8 plus 35 mesh. It

can also be used in the size range usually handled in froth flotation processes, i. e., minus 35-48 mesh to fines. Thus the present process is applicable to a wider range of particle sizes than is a conventional process of froth flotation.

In addition, it is simply and readily operated, normally requires less apparatus and is more economical in operation.

The problem of slime is not greatly different than in froth flotation processes. In the case of the present invention, as elsewhere, slime is never desirable. However, it is an advantage that the agglomerating agents may be chosen from a wide variety, some of which are less affected by slimes than others. Thus it is possible to treat undeslimed ores, partially deslimed and thoroughly deslimed ores, the choice depending upon various factors. The effect of slimes is noticeable primarily in added consumption of the agglomerating agent. As the preferable 00 agents of this invention are not expensive, it

may be advantageous to not deslime or to remove only the colloidal fractions and use more reagents. The extent of desliming is therefore one of economic compromise and must be determined in the case of each ore.

So far as the efliciency of the chemical pretreatment is concerned, it may be carried out in pulps of either low or high density. The choice may vary somewhat with the chemical agents used but actually depends principally on the apparatus used. Conditioning may be carried out in a type of rolling drum, or an open tank having a mechanical impeller therein, or any other apparatus capable of eilicient mechanical agitation 76 and mixing. The use of a tank and impeller, for

low density. usually 25% of limitation. All

I; On the other hand, it may be desirable to condition the pulp in an agitator similar in construction to the conventional, mechanical type flotation machine such as the well-known Fagergren or Denver cells. This ordinarily requires pulps of or less solids. This, except for the necessity oi handling larger pulp volumes. is not particularly disadvantageous since most of the preferred reagents are about equally effective when conditioned at either high or low solids.

n the other hand. the disadvantage in handling larger pulp volumes may be often far more than offset by the advantage or being able -to introduce small amounts of line air bubbles into the pulp during agitation. Presumably each small discrete air bubble becomes surrounded eration of the magnetic and non-m gnetic material. This should not be confused with the frothing produced by purposely introducing large volumes of air during froth flotation operations. The amount oi air introduced according to the present process is only a fraction of that used in ordinary practice of froth flotation. Because of the extremely minute air bubbles which it is capableof introducing, a conditioner employing the-Fagergren type rotor and stator is preferable for this purpose.

After being conditioned with the agglomerating agent, the conditioned pulp is then subjected to magnetic separation. This can be carried out in any of a number of'conventional machines which are commercially available for the purposefor example, the well known Steflensan and Crockett separators. are ordinarily necessary except that in those cases where the conditioning step is carried out at very high solids, it is usually desirable to dilute 45 No particular precautions with treated particles, thus assisting in agglom- I r of Test 1 of Example 1,

was made directly into an aqueous pulp of about 25% solids and subjected directly to magnetic separation. Further, in order to show the ineifectiveness of carrying out a conditioning step with a fatty acid as taught by the prior art. the second sample was before the magnetic treatment the pulp was conditioned for two minutes with 2 Ila/ton of oleic acid. From the results shown in the following Table I, it will be noted that this procedure gives a slightly poorer grade and very little better recovery than when the step was omitted entirely.

I Table I Asssymerccnt I Tm Percent Product 55.3 Digit.

Fe Insol.

Exmru 2 In order to show the comparative eifectiveness of conditioning with the reagents of the present invention rather than the fatty acid of the prior art, a number of additional samples of the same ore used in Example 1 were treated according-to the process of the present invention by conditioning an aqueous pulp of the ore containing about 70% solids for 2 minutes with the reagents, diluting the pulp to about 25% solids, and then subjecting the pulp to magnetic separation. The reagents used and the metallurgical results obtained are shown in Table II. 7 It will be seen that whereas the grade is substantially that obtained when no conditioning step the recovery was increased as much as to This increase in recovery is very important since the improvement magnetically susceptible iron minerals.

treated in the same way except tint is used, as in the case- Table II 1 Assay, Per Cent Dumb Reagents Product as? Per Cent Fe Insol. Fe Lbs/ton Type Head 100. 00 54. 95 100. 00 2. 0 Sulfuric acid. l Concentrate... 74. 24 65. 74 3. 52 88. 82 2. 8 Oil-soluble troleum sulionate. Telling 25. 76 23. 80 ll. 18 3. 9 1 Fuel oil, 2253c.

Head 100. 00 54. 83 100. 00 l. 5 Sulfuric acid. 2 Concentrate... 60. 13 65. 36 70.48 2. 8 Water-soluble petroleum sulionate.

Tailing 40. 87 39. 60 29. 52 6. 2 Fuel oil. Head 100. 00 54. 49 100. 00 l. 6 Sulfuric acid. 3 Concentrate 58. 94 65. 15 4. 56 70. 47 3. 3 Sulfonated talloel.

Taiiing 41. 06 39. i9 29. 53 5. 8 erosene. Head 100. 00 54. 63 100. 00 2. 5 Sulfuric acid. 4 Concentrate... 66. 91 65. 18 5. 36 67. 90 3. 5 Oil-soluble petroleum sulionate.

Telling 43. 09 40. 32. 10 r the pulp before subjecting it to the magnetic separation.

The invention will be more fully described in conjunction with the following examples in which the purpose is illustrative only and not by way parts are by weight unless otherwise noted.

Examu: 1

In order to show the eilect of magnetic separation alone without the conditioning operation, a sample of a beneficiation plant product contain-.

- ing magnetite, marti-te, and a quartz gangue was divided into a number of samples. One sample 70 the procedure of Example In order to demonstrate that the process may be operated successfully in neutral or alkaline circuit and that conditioning may be conducted at low solids, the following example was carried out:

Exmru 3 Several additional samples of the same are used in previous examples were treated according to 2 except that the pulp was directly 'made up at about 25% solids and the conditioning step carried out at that pulp density. No acidifying agent was used except in the last test. It will be seen that the results compare very favorably with those obtained in Example 2. The metallurgical results and the reagents are shown in Table III.

Table III Assay, Per Cent Dumb Reagents Product ag? Per Cent Fe Insol. LbsJton Type Head 100. 55. 78 100- 00 2. 0 Sulionated olelc acid. Concentrate. 60. 57 66. 65 3. 82 79. 55 7. 0 22 B6. fuel oil. Telling 33. 43 34. 12 20. 45 He 100. 00 55. 92 100. 00 4. 0 Sulionated refined talloei.

75. 12 65. 28 6. 44 87. 69 5. 3 Kerosene. Tall 24. 88 27. 66 12. 31

100. 00 55. 25 100. 00 5.0 Sulfuric acid.

60.14 65. 18 5. 34 70. 05 4. 0 Oil-sol. pet. sulionate. 39. 86 40. 27 29. 05 4. 4 Fuel oil.

EXAMPLE 4 A composite of an iron ore washer plant tailing 2o EXAMPLE 6 and a magnetite ore was ground and partially deslimed by hydraulic classification. Two samples of the sands were taken and the first subjected directly to magnetic separation as a pulp of about solids. The second was conditioned for ,2 minutes at about 70% solids with 1.8 lbs./ton of sulfuric acid, 3.2 lbs/ton of an oil-soluble petroleum sulfonate, and 5.1 lbs/ton of fuel oil and then was diluted to about solids and subjected to magnetic separation. The magnetic concentrate was diluted to about 20% solids and cleaned magnetically. The results obtained are shown in Table IV.

Table IV Per cent Product weight Telling EXAMPLE 5 In order to illustrate the treatment of ores which do not naturally contain a magnetic constituent, the following treatment of a hematite ore was carried out. In the first test, a sample of minus 10 plus 65 mesh ore was admixed with about 16% (by weight) of magnetite and the mixture was conditioned for solids with 7.7 lbs./ton of sulfuric acid, 6 lbs./ton of an oil-soluble petroleum sulfonate, and 7.5 lbs/ton of fuel oil. The conditioned pulp was diluted to 25% solids and subjected to magnetic separation. In the second test, only 8% of magnetite was added and only 5.9 lbs/ton of sulfuric acid was used, the procedure being otherwise the same. Illustrative results are shown in Table V.

Table V Assay, per cent Di i Test Per cent No. Product Weight Per cent Fe Insol.

cad 100. 00 53. 97 100. 00 1 Concentrate 86.15 57.66 13. 92.04 T 13.85 31.02 7.96 H ad 100.00 53.20 100.00 72. 58. 91 10. 80. 45 27. 35 38. 02 19. 55

2 minutes at high ISO A washer tailing from the Mesabi range containing principally hematite and quartz and assaying about 23% Fe was partially deslimed by hydraulic classification and then was mixed with a magnetite concentrate in the ratio of about 3.1 to 1.0. This pulp was then conditioned for 2 minutes at high solids with 7.2 lbs/ton of sulfuric acid, 4.3 lbs/ton of an oil-soluble petroleum sulfonate, and 4.8 lbs./ton of fuel oil; diluted to about 25% solids and subjected to magnetic separation. The concentrate was cleaned once. The results are shown in Table VI.

Table VI Assay, Per Cent Distrib.

Product Per Cent Per Cent Wt. Fe

Fe Insol.

EXAMPLE '1 A New Jersey magnetite-martite ore assaying about 13% iron, the major portion of the iron being present as a non-magnetic oxide, was ground for 12 minutes in a rod mill and then diluted to about 25% solids. This pulp was divided into two samples. The first was directly subjected to magnetic separation and the magnetic concentrate cleaned once magnetically. In the second test, the colloidal fraction was removed by hydraulic classification and the sands conditioned at high solids with 2.0 lbs/ton of sulfuric acid, 2.0 lbs./ton of an oil-soluble petroleum sulfonate, and 1.7 lbs/ton of fuel oil. The conditioned pulp was subjected to froth flotation and the resultant rougher concentrate given a single cleaning by flotation. The cleaned concentrate was then diluted to about 25% solids and subjected to magnetic separation. This produced a high grade concentrate and a relatively high grade middling which itself can be subjected to any further desirable treatment such as tabling and the like. This procedure was used to illustrate the adaptability of the present process in conjunction with standard procedures of froth flotation. The results are shown in Table VII.

Table VII Assay, per cent m t lb Test Per cent a r Product Weight PerFcmt Fe Insol.

Exsmtn -8 Another portion of the same ore used in Example '7 was ground and partially deslimed by hydraulic classification to remove the colloidal fraction. By the same treatment used in the second test of Example 7, the sands were then conditioned with various reagents and subjected directly to magnetic separation. The reagents used and the results obtained are shown in Table VIII. It will be seen that the results obtained are superior to those of the direct separation without the conditioning obtained in Test 1 of Example '7.

Table IX Assay, per cent Di strib.

'lllzest Product Per cent Per cent 0. Weig Fe Fe Insoi.

100. 00 22. 87 100. 00 15. 23 66. 49 7. 02 44. 27 4. 59 27. 68 5. 56 80.18 V 14.31 50.17 100. 00 23. 82 100. 00 7.36 8.60 2 66 31.13 64.32 9. 72 84.07 6. 21 10. 03 2. 61 55. 4. 60 10. 66 100. 00 23. 58 100. 00 10. 05 9. 90 4. 2 3 22.84 69.86 5. 04 67.68 g. :3 4;: g 26. 22 17. 3g

1. Polling 54. 58 4. 12 9. Combined Concs 31. 57 63. 10. 90 85. 17

I claim:

1. A method of concentrating oxidized iron mineral values from mixtures thereof containing acidic gangue and both magnetic and non-mag'- netic iron oxides, which comprises the steps of making an aqueous pulp of the solids of suinciently small size to insure liberation of the mineral values. conditioning the aqueous pulp with an agglomerating agent combination comprising a material selected from the group consisting of sulfonated long-chain aliphatic fatty acids, sul- Table VIII Assay, Per Cent Dismb Reagents Test Product Per Cent Per Cent g 1 No. Wt. Fe

v x Fe Insol. Lbs./ton Type Head 100. 00 13. 38 100. 00 lime 6. 01 6. 86 3. 08 2. 0 Sulfuric acid. l. Mag. (50110.... 15.61 55.83 65.11 2.0 0il-sol.pet.sulionate. 7

Cl. TalL- 3. 80 15. 11 4. 29 1. 7 Fuel oil. Tailing 74. 58 4. 94 27. 52 Head 100. 00 13. 23 100. 00 Slime 6.04 7.32 3. 34 3.0 Sulfuric acid. 2 Mag. 00110..-. 14.64 59.84 66. 23 3. 0 Oil-sol. pet. suli'onate.

Cl. Tail 2. 84 16. 50 3. 54 Telling 76. 48 4. 26. 89

EXAMPLE 9 fonated saponifiable oils of animal and vegetable with 4.0 lbs/ton of sulfonated refined talloel and 6.2 lbs/ton of No. 2 fuel oil. The pulp was subjected to a magnetic separation and the concentrate therefrom was conditioned without additional reagents for /2 minute and given a magnetic cleaning. The third portion was given the same treatment as the second except that the reagents used were sulfuric acid, 3.0 lbs./ton, and an oil-soluble petroleum sulfonate, 3.0 lbs/ton, and 22 .B. fuel oil, 4.4 lbs/ton. The rougher concentrate was given a magnetic cleaning. The cleaned concentrate was conditioned for 5 minutes at low solids with 3.0 lbs./ton of soda-ash and 0.35 lb./ton of quebracho to release the floccules, and the treated concentrate was then magnetically separated to recover the magnetite. The non-magnetic remainder was designated as the martite concentrate. The results are shown in Table IX.

origin, sulfonated talloel, sulfonated'naphthemc acids, petroleum sulfonates of the oil-soluble mahogany acid and water-soluble green acid types obtained in the refining ofpetroleum lubricating oils, mixtures of these petroleum sulfonates and salts of these materials, together with an unsaponifiable oil, in amount suflicient to insure thorough dissemination of the sulfonated reagent,

and, at least in the case of the petroleum sulfonates, a material selected from the group consisting of acids and materials liberating an acidic substituent in solution, having a dissociation constant greater than l0-' and used in sufficient amount to produce a .pH of about 5.5-1.5; subjecting the conditioned pulp to a magnetic separation whereby a. magnetic concentrate is removed comprising the magnetic substituents and a major portion of the desired non-magnetic substituents.

2. A process according to claim 1 in which the magnetic concentrate agglomerate is broken up,

and the so treated concentrate is subjected to a magnetic separation whereby a magnetic concentrate comprising the magnetic substituents is removed and at least a part of the magnetic concentrate so removed is admixed with fresh feed prior to the agglomerating operation.

3. A process according to claim 1 in which the aqueous pulp of the mixture to be treated is conagglomerating reagent combination comprises v fuel oil and a sulfonated fatty acid.

5. A process according to claim 1 in which the agglomerating reagent combination comprises sulfonated talloel and a fuel oil.

6. A process according to claim 1 in which the agglomerating reagent combination comprises a strong inorganic acid, a fuel oil, and a petroleum sulfonate selected from the group consisting of the oil-soluble, mahogany acid and water-soluble green acid types, obtained in the refining of petroleum lubricating oils, mixtures thereof and salts of these sulfonates. I

7; A method of beneflciating ores containing oxidized iron mineral values and acidic gangue, the iron mineral values being present as both magnetic and non-magnetic oxides which comprises the steps of making an aqueous pulp of the solids of sufllciently small size to insure liberation of the mineral values, conditioning the aqueous pulp with an agglomerating agent combination comprising a material selected from the group consisting of sulfonated long-chain aliphatic fatty acids, sulfonated saponiflable oils of animal and vegetable origin, sulfonated talloel, sulfonated naphthenic acids, petroleum sulfonates of the oil-soluble mahogany acid and water-soluble green acid types obtained in the refining of petroleum lubricating oils, mixtures of these petroleum sulfonates and salts of these materials, together with an unsaponiflable oil, in amount suflicient to insure thorough dissemination of the sulfonated reagent, and at least in the case of the petroleum sulfonates a material selected from the group consisting of acids and materials liberating an acidic substituent in solution, having a dissociation constant greater than 10" and used in sufficient amount to produce a pH of about 5.5-1.5; subjecting the conditioned pulp to a magnetic separation whereby a magnetic concentrate is removed comprising the magnetic substituents and a major portion of the desired non-magnetic substituents.

EARL CONRAD I-IERKEN HOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 933,717 Lockwood Sept. 7, 1909 1,043,850 Lockwood Nov. 12, 1912 2,069,182 Hagood Jan. 26, 1937 QTHER REFERENCES Ref Le Genie Civil Tome XCIII No. 14, pages 328 to 330, Oct. 6, 1928. 

